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我是 C++ 的初学者，我的一个项目涉及循环内循环和创建随机数。这是我到目前为止所拥有的：`

using namespace std;

int main()
{   
    srand((unsigned int)time(0));

{
    cout << "Name of reservoir: ";
    string reservior_name;
    cin >> reservior_name;

    cout << "Capacity in MAF: ";
    double capacity;
    cin >> capacity;

    cout << "Maximum inflow in MAF: ";
    int max;
    cin>> max;

    cout << "minimum inflow in MAF: ";
    int min;
    cin >> min;
    if(min>max)
    {cout<<endl<<"Error: The minimum inflow is higher than the maximum inflow."<<endl
         << "Please re-enter your minimum inflow: ";
    cin>>min;
    }
    double inflow_range= max-min;

    cout <<"required outflow in MAF: ";
    double required;
    cin >> required;
    if (required > 0.9 * (min + max)/2)
    {
        cout<<endl<< "Warning: required ouflow is over 90% of the average inflow."<<endl
            << "Returning to main menu ";
    }
    else
    { const     int simulations = 10;
                int water_level = 0;
                int years = 1;
                cout << "Running simulation..." << endl;
                for (int i = 1; i <= simulations; i++) 
                {
                    int x = (rand()% (max-min + 1)) + min;

                    while (water_level < capacity)
                    {
                        //double r = rand() * 1.0 / RAND_MAX;
                        //double x = min + inflow_range * r;
                        //int x = (rand()% (max-min + 1)) + min;
                        if (water_level + x > required)
                        {
                        water_level = water_level + x - required;
                        }
                        else
                        {
                            water_level= 0;
                        }
                        years++;

                    }   
                cout <<"Simulation "<< i <<" took " << years <<" years to finish"<< endl;
                }
    }
}
system ("pause");
return 0;       
}
`

所以我的主要问题是我遇到了关于在“运行模拟”下设置 for 循环的问题，我需要设置第一个 for 循环以运行内部 for 循环 10 次，其中每 10 次迭代内部 for 循环为随机值查询的可接受结果范围提供随机数。有人告诉我这个想法是使用蒙特卡洛方法，即我把蒙特卡洛方法和正常随机数生成方法都放在这里。这里是：

for (int i = 1; i <= simulations; i++) 
                {
                    int x = (rand()% (max-min + 1)) + min;

                    while (water_level < capacity)
                    {
                        //double r = rand() * 1.0 / RAND_MAX;
                        //double x = min + inflow_range * r;
                        //int x = (rand()% (max-min + 1)) + min;

所以程序将为流入创建一个随机值。这个想法是内部 for 循环将继续运行，直到从 0 开始的水库的 fill_level 达到容量。模拟多少年的过程（内部for循环的每次迭代代表一年）由water_level模拟for循环的父for循环重复10次。

问题是应该创建的随机数是相同的数字。每次我运行它时它们都不同，但每次循环重复以进行新模拟时它们都是相同的。几个小时以来，我一直试图找出问题所在，但仍然卡住了。非常感谢任何帮助。

4

2 回答 2

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在您的x代码中是随机的，问题是之后的算法和计算。实时查看您的代码。

您忘记在每次迭代时重置模拟参数，将这些放在模拟循环中：

--------------------------------------------+
                                            |
for (int i = 1; i <= simulations; i++)      |
{                                           |
  int water_level = 0;                   <--+
  int years = 1;                         <--+
  int x = (rand() % (max - min + 1)) + min;

见本版后代码：live code。输出是

Simulation 1 took 68 years to finish
Simulation 2 took 101 years to finish
Simulation 3 took 8 years to finish
于 2013-05-20T06:32:37.087 回答
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x使用如图所示的代码，每次迭代（模拟）都会为模拟的所有年份获得一个单一的值。您注释掉的代码x每年都会生成一个新值。你想要哪种方法？我倾向于认为流入量每年都在变化，因此您应该为每年生成一个新值x。

看起来您应该为每个模拟重置years和water_level。

cout << "Running simulation..." << endl;
for (int i = 1; i <= simulations; i++) 
{
    int water_level = 0;
    int years = 1;

    while (water_level < capacity)
    {
        int x = (rand() % (max - min + 1)) + min;
        if (water_level + x > required)
            water_level += x - required;
        else
            water_level = 0;
        years++;
    }
    cout <<"Simulation "<< i <<" took " << years <<" years to finish"<< endl;
}

对于调试，我想打印控制参数（min, max, capacity, required），然后在内循环的每次迭代中打印关键值（ year, x, ），直到我满意它工作正常。water_levelwhile

于 2013-05-20T06:38:15.187 回答